Multi-dimensional sonic recording and playback devices and method

ABSTRACT

A method and apparatus for recording sonic material so that it may be used to achieve accurately a multi-dimensional playback sonic effect highly similar to that of the original material experienced in the playing volume such as that of an auditorium, studio or theater and accomplishing this in volumes which do not necessarily duplicate the recording location. A novel enclosure which may be used as a high gain type planal microphone enclosure is disclosed as well as a system of recording/playback which incorporates delimiting the recording and playback space in such a manner that the volume of the original recording space may be duplicated by means of selectively time delaying various channels of a recording system relative to each other.

United States Patent [191 Murry 154] MULTI-DIMENSIONAL SONIC RECORDINGAND PLAYBACK DEVICES AND METHOD [75] Inventor: Edward J. Murry, PalosPark, Ill. [73] Assignee: Fibre-Sonics, Inc., Chicago, Ill.

[22] Filed: March 6, 1970 [21] Appl. No.1 17,079

[52] U.S. Cl ..179/100.l TD, 179/1 G, 179/15 BT, 179/1002 MD, 179/1002RE, l79/l00.3 B,

[51] Int. Cl ..Gl1b 21/00, G1 lb 23/18, H04h 5/00 [58] Field ofSearch....179/l00.1 TD, 100.2 RE, 1 G, 179/15 BT,100.2 MD, 100.3 B;181/31 B [56] References Cited UNITED STATES PATENTS 2,831,069 ,4/1958Snow ..l79/l00.2 RE

3,158,695 11/1964 Camyas ..l79/100.l TD 3,203,502 8/1965 Rife v ..l8l/31B 3,360,073 12/1967 Murry..... .....l8l/3l B 3,375,329 3/1968 Prouty..179/1 G 3,538,265 11/1970 Keeler ..l79/l00.2 RE

1 1 Jan. 9 1973 FOREIGN PATENTS OR APPLICATIONS 604,080 4/1960 ltaly"179/1001 TD 1,025,292 4/1953 France ..l79/l00.l TD 1,196,711 7/1965Germany ..l79/l G Primary Examiner-Stanley M. Urynowicz, Jr: AssistantExaminer-Raymond F. Cardillo, Jr. Attorney-Hill, Sherman, Meroni, Gross& Simpson [57] ABSTRACT A method and apparatus for recording sonicmaterial so that it may be used to achieve accurately a multidimensionalplayback sonic effect highly similar to that of the original materialexperienced in the playing volume such as that of an auditorium, studioor theater and accomplishing this in volumes which do not necessarilyduplicate the recording location. A novel enclosure which may be used asa high gain type planal microphone enclosure is disclosed as well as asystem of recording/playback which incorporates delimiting the recordingand playback space in such a manner that the volume of the originalrecording space may be duplicated by means of selectively time delayingvarious channels of a recording system relative to each other.

10 Claims, 23 Drawing Figures PATENTEUJAN 9197s SHEET 2 OF 7 f3 HY@Wwumum PATENTEDJAN 9 I975 SHEET 5 BF 7 INVENTOK flzaerdJ/fzz PATENTEUJAN 9 I973 SHEET 6 OF 7 146 INVENTOR \TTOR.VE Y8 MULTI-DIMENSIONAL SONICRECORDING AND PLAYBACK DEVICES AND METHOD CROSS REFERENCE TO RELATEDINVENTIONS My prior US. Pat. No. 3,360,073 entitled LOUD SPEAKERENCLOSURE which issued on Dec. 16, 1967, discloses a speaker which whenmounted in a comer of a room formed, by example, by the ceiling and twoadjoining walls creates the efiect on a listener in a room of beingsurrounded by a sound emanating from the speaker. This patent disclosesan apparatus for the projection of sound but can be modified and used inthe present invention for recording as well as the projection of sound.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates in general to sound recording and reproduction. Numerous patentsand articles have disclosed devices and systems of speakers, or ofspeakers/amplifiers microphones in combination which have as theirobjectives the faithful reproduction of the original sonic materials ata location other than the recording location. Such multi-dimensionalsound has been called stereo" (meaning solid), high-ti, or 3-D sound.Yet, most of these systems approached the problem as if it were merely2-dimensional in nature and as if it were taking place in an area, e.g.the listening area. Actually all sound takes place in volumes and not inareas of space; and these all have 3-dimensional characteristics ofresonance, reverberation, absorption, and many other characteristics,which not only can, but do change the sound that comes from anyradiator, or which arrives at any receptor, most drastically. My priorUS. Pat. No. 3,360,073 describes a method and apparatus whereby it ispossible to achieve I l-dimensional coupling to a 3-dimensional spacewith effectiveness, efficiency and fidelity which was superior to priormethods. My prior patent however, did not give the mathematical basisfor a complete understanding of the theoretical work resulting in thatinvention. In addition, quantitative reduction to practice of thatinvention has resulted in a superior understanding of the mechanismswhich are at work and of further applications of the principles involvedwhich have resulted in further inventions and applications; one of whichis the use of the principles in a superior microphone encasement andsonic input-conditioner.

2. Description of the Prior Art There exist several severe nomenclaturalerrors in sound production fields regarding pickups and loud speakers(not the least of which is the latter word, i.e., loud speaker, whichshould be called at the least, a loud-sounder). One prevalent error hasbeen in the almost complete use of the narrow Z-dimensional concept ofthe listening-area when what is actually meant is the listening-volume,since sound is reflected from all available surfaces including floorsand ceilings. Another error, due to the failure to appreciate and usethe volume concept rather than the area concept, is the present idea ofstereo sound, wherein two sources of essentially point-source sound aresupposed to create a sonic solidity (stereo), in 3- dimensions. As amatter of fact this idea has been proved erroneous time after time byseveral acoustic engineers. Also, in existing systems many compromisesare made between the accuracy of the left-to-right spacing and nothingwhatsoever is done about the front-to-back spacing, or to the everpresent third dimensional modeling of this type of sound which isurgently required.

For many years it was felt that the objective was to create a wall ofsound based on the concept of 2- dimensionality. The erroneous mixing ofsound components in a temporal/spatial hodgepodge of relationships, fromleft-to-right, and from front-to-back, even by some advocates ofso-called surrounding stereo, is crude, inadequate and not, in fact,true sculpturing of the sound to a solid sound (stereo). One of theweakest links in the entire science has been the consistent failure toadmit that sound is truly a 3-dimensional, or true volume phenomenonalthough authorities such as Olson clearly states and shows, as inAcoustic Engineering of October, I964 at page 4, that the general caseof sound propagation involves three dimensions.

SUMMARY OF THE INVENTION The present invention allows the design andconstruction of a recording and reproduction system which implicitlyobeys the general equations of sonic propagation in 3-dimensional space.A novel recording means for similar reproduction of sonic material isprovided and a system and apparatus is provided for accurately achievinga multi-dimensional playback sonic effect highly similar to the originalmaterial experienced in the playing volume such as an auditorium, studioor theater and to accomplish this regardless of the dimensions of theplaying-back volume. Various apparatuses for recording and playback inwhich multitracks, that may be individually adjusted, are provided sothat the phasing of various signals may be accomplished in order toprovide a replica of the original sound in a volume which differs fromthe volume of the recording location.

Other objects, features and advantages of the invention will becomereadily apparent from the following description of certain preferredembodiments thereof taken in conjunction with the accompanying drawings,although variations and modifications may be effected without departingfrom the spirit and scope of the novel concepts of the disclosure and inwhich:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a typicalsmall room provided with the present invention;

FIG. 2 is a sectional view of a novel pickup microphone according to myinvention;

FIG. 3 is a plan view of a recording chamber illustrating the invention;

FIG. 4 illustrates a recorder for reproducing sound according to thisinvention;

FIG. 5 illustrates a playback mechanism according to the same invention;

FIG. 6 illustrates a recording room;

FIG. 7 illustrates the base relation among various signals in therecording room of FIG. 6',

FIG. 8 illustrates a playback volume;

FIG. 9 illustrates a phase relationship in the playback volume of FIG.8;

FIG. 10 illustrates a special illustrative recording system of theinvention;

FIG. 11 illustrates a similar playback system of the invention;

FIG. 12 illustrates a special tape recorder for recording and playback;

FIG. 13 illustrates a sideview of the tape to be used with the machineof FIG. 12 to show the 4-tracks used;

FIG. 14 illustrates a magnetic recording disc with recording andplayback mechanism;

FIG. 15 illustrates a magnetic recording and play back drum;

FIG. 16 illustrates a generally pie-shaped recording auditorium todemonstrate a complex situation;

FIG. 17 illustrates a typical listening volume converted to anequivalent pie-shape;

FIG. 18 illustrates the inventionas applied to regular dual-track disctype recording;

FIG. 19 is a multiple stylus holder for the disc of FIG. 18;

FIG. 20 is a schematic view of the microphone or loud-speaker enclosureof this invention or of US. Pat. No. 3,360,073;

Flg. 21 is a side view of the microphone or loudspeaker enclosure;

FIG. 22 is a plot of sound waves versus time; and

FIG. 23 is another plot of sound waves versus time.

DETAILED DESCRIPTION OF THE INVENTION My prior U.S. Pat. No. 3,360,073discloses a 3-surface corner sound radiator for mounting at the ceilingat a junction of two walls and which has adjustable control vents ateach of its three corners. FIGS. 20 and 21 illustrate such a radiatorwith corner vents a, b and 0. Such a 3-surface corner radiator, built asshown obeys the classical 3-dimensional space matrix configuration inwhat I designate w (omega) space and tr (pi) space inter-operations.

The equation of continuity states that: The amount of matter entering(0" space equals the increase in matter inside this contained volume ofspace.

It can be assumed that the influx and efflux through the ports a, b andc is analogous to that which would enter from the x, y, and 2dimensions. Hence, since, Ax, Ay, Az equals the permitted Aa, Ab, Ac,then the difference between the influx matter and the efflux matterwould be:

where a, b, c, equals the coordinates of a particle in the commonmedium; u, v, w, equals the component velocities of the particle in themedium; and e equals the static density of the medium.

The rate of growth of the gas mass in the 0 space volume 6el8t Aa Ab Ac,is equal to the above expression, or in time units:

I I I I ai+lH e u v E w =Owhere z=time 6t Ba 6b dc and it can be seenthat the three dimensionality of space is obeyed, as is the conservationof matter, hence this system will react to these facts implicitly, andall the acoustic wave equations are valid since the revent ports (a, b,c) are oriented in such a manner as to be aligned in x, y, and 1dimensions, and the system obeys implicitly the conservation of matterlaw, and the 3- dimensionality of space energy propagation laws.

The important point is that energy transfer from D" (the energygenerator) to 'n' space (which generator also occupies an space) canonly be done with proper 3-dimensional obedience if 1r space and tospace are coupled in such a manner as to preserve their correctinterrelation. Ports a, b, and c being present, and properly oriented dothis, while all other systems cannot do this completely since usuallyonly one of the dimensional components (1, y, or z) are coupled fromtheir 00 space to their 11' space, or even no coupling is used.

Since motion (referring to Ax, Ay, Az) changes 0: space, it is foundthat the acceleration of momentum parallel to x, is e Ax Ay Az Sta/6t(as is the acceleration of momentum parallel to y and z with simply achange in symbols) Then the mean pressure on the face perpendicular tothe x (or y or z) dimension is:

5w I as? AyAz and (to AyAz and for the y dimension:

net; (60 6y )AxAz and for the z dimension:

i ali and (0+ )AxAz a I m (0 Am and (E0 860 A2 a2 2 )AxAy (when so thepressure in the media.)

The difference in so being a force Sea/8x Ax Ay Az, or Sea/8y Ax Ay Az,or Sea/8: Ax Ay Az in the increasing x dimension (or in the increasing yand 2 dimensions) and in the direction of increasing x (or y or z). Theequation of motion for a three dimension space then becomes:

which can be simplified to: dVuvw/d! l/e Grad. so 0.

Obviously, sound pressure (eo') can only obey the conservation ofmomentum and act in 3-dirnension space, if the x, y and z componentsco-act between in space and 1r space.

Since the media of propagation is a gas under rapid compression andexpansion due to the sound waves present, the temperature of the mediavaries adiabatically, and it has been shown elsewhere that:

( (l ratio)"= l v. ratio or: so so 07 ratio, and the excess(instantaneous pressure) sound pressure P equals co 'yratio, or P= e07e'-s/e.

All the above applies for a perturbation of the media by sound waves ofany amplitude and it is to be noted that the rate of growth of the mass,and the equation of motion for the mass, is non-linear, if theamplitudes are large; hence, must be non-linearly provided for, whilethe compressibility of the gas equation is linear and can be readilyhandled regardless of amplitude.

The saving factor for acoustic waves are their comparatively smallpressure amplitude (compared to the pressure of the atmosphere), and thewavelength being relatively large, hence, u, v, w, and the ratio e-e/echange very little in their x, y and 2 travels.

Since this is true it follows (from DAlembertons wave equations) thatthe equation for the velocity of propagation of sound in a media is:'yeole C velocity squared where,

'y= 1.4 (for air) so the static pressure with no sound present (indyneslcm e the density of the medium of transmission.

and we must critically note that for sound in air 7 is fixed at 1.4, asis the value of 0, hence, the velocity of propagation, and all otherparameter related backwardly with the above, is a function of thedensity of the media, which is varying directly in front of thediaphragm in 7r space and behind the diaphragm in (0 space. Thus, thevelocity of sound is different at all times to the front and rear of ourspeaker diaphragm (and in all moving cone speakers) and compensation forthis fact must be provided in some manner.

The problem therefore becomes simply a case of the proper control of thepressure to the rear, and to the front of an electrically drivenmechanically oscillated diaphragm, which produces wave motion in thechosen medium in which it is operated.

In the actual operations of the tri-surface, tri-portalsound-conditioner enclosure, we observe that the volume to the rear ofthe sonic generator (the diaphragm 11) is exactly prescribed, and isexactly determined due to the air being sealed into the rear at eachedge by a rubber seal; however, the revent ports a, b and c provideescape for the air and are of a definite length and cross sectionalarea, both of which are variable, and are carefully oriented in the x, yand z axis. These are made of acoustically dead material, so as not toadd-to or subtract-from the frequency components of the sound that isdesired, and which is present in the feedback wave sample as it passesthru these ports.

When the diaphragm l 1 moves forward momentarily under the influence ofan input of electrical energy into the voice coil of the speaker, aslight vacuum is created to the rear of it, while a positive pressureappears at its front surface. This latter is not permitted to escapeinstantly, but is critically controlled in its behavior by the soundconditioning cone in its pathway, which is so designed of selectedlaminating materials of various sonic absorbing or reflective abilitiesso as to provide conditioning of the sound on a frequency selectivebasis. Further, it provides a precisely calculated loading to thepressure front. As the wavefront moves outward, part of its x, y and 2components find pressure relief ports properly oriented in theirpathways (note that I purposely feedback components of the x and y, they and z and the z and the x complex wave). Controlled samples of the xand y, the y and z and the z and x components are permitted to return tothe rear of the diaphragm to alleviate the vacuum there present. Thephase/time variations of this unloading wave may be controlled by thelength of the tubes a, b and 0. By controlling the cross sectional areaof these same tubes, the amount or quantity of the unloading iscontrolled. The total amount of unloading experienced is of course equalto the sum of the three port areas, times the size of these areas, whichare usually varied by selective insertion of various tubes of decreasingdiameters.

Thus, we have devised an acoustic analog of negative-feedback, soimportant to amplifier linearity, and as might be expected this negativeacoustic feedback also provides increased sonic linearity, equivalent tothat of the many RC circuits used in various amplifiers; the tube lengthbeing equivalent to the resistance (R), while the tube diameter isequivalent to the capacity (C), of such type circuits.

In the above, we can see that the loading/unloading cycle behavessimilarly if the diaphragm moves backward, wherein the positive pressureappears at the rear of the diaphragm, and an instantaneous vacuumappears at the front. As these variations take place, it is to be notedthat the greater that the to and fro movement becomes, the greater isthe pressure (or vacuum) generated and that it will follow the nonlinearcompressibility of the transient air cushion prevailing at any giveninstant of time. This is done dynamically by a static system of acousticnegative feedback built up of static parts. It provides for severeelectrical driving of the one moving part (the diaphragm 11) withoutdistortion appearing in the air wave or without the so-called breakup ofthe cone appearing. One can operate the diaphragm air-driver to thelimits of the available power of the associated amplifier withoutdistortion appearing, since it always looks into the proper loading atall times. In this manner, one may use all of the power available andhave no need for purchasing excessive amounts.

Referring to the previous equations for a moment, the significance canbe seen of the prescribed volume concept being to the rear of the conedriver, to the conditioning cone concept (for selective absorption andreflection of various frequencies), to the vital principle of samplingthe x and y, the y and z, and the z and .1: components, then using theseas acoustic negative feedback for the automatic variations in time ofthe instantaneous pressures and vacuums which appear so transiently atany given moment.

It should be noted that while the ear can detect and instantly noticethe increased fidelity, clarity and intelligibility of the eminent soundfrom this system, when properly designed, it is quite difficult tomeasure this on most electronic instruments, unless one knows what isbeing done, and uses special methods, based on the transient responsesof the system.

As seen from above, the simple seeming enclosure, shown in my U.S. Pat.No. 3,360,073, is not simple and is indeed the only speaker whichimplicitly recognizes the three dimensionality of the sonic problem, andby its proper placement, its conditioning effect, and most of all, byits use of the revent ports a, b and c (which are reallynegative-pressure feedback devices, designed to control the efflux andinflux of pressure variations in the particle flow from the front toback of the speaker, thereby controlling the loading and unloading ofthe piston) operates in such a manner as to automatically control itsown excursions, precisely and at all levels of sonic drive, and that itsunique tri-surface design insures the rapid. formation of a truespherical-segment wavefront. As this is formed, it spreads out from itsupper-corner location, maintaining all its spherical 3- dimensionalaspects, into the listening volume. Even this wavefront is somewhatdegraded by the varying refraction, diffraction and absorption near itsedge, but not anywhere near to that of all other systems. A momentsvisualization will show why this is true and of importance. With sonicwave lengths present (in small chambers) of 55 feet, in 1 cycle oflength (20 cycles per second) which takes but ll 100th of a second totravel across a 10 foot room, we can see immediately thatstereo-modeling of the sound by a single point source is most difficult.The addition of another radiator according to my patent in one of theother upper corners, will behave similar to the number one speaker; but,in addition, it will provide a most excellent stereo effect (a simulatedspatial effect since no part of the wave will be out of phased,3-dimensional relationship). Even when very large separations are used,due to the tight coupling to the walls and the ceiling, the stereoeffect is not choppy, but startlingly lifelike. Measurements which havebeen made, have shown the sound characteristics to be about 30 percentsimilar to that of recorded tests made in the same room with a livesource of sound present. By that is meant that the phased components ofthe various complex segments are present in proper spatialrelationships. Tests on other systems showed less than percent spatialpreservation of the characteristics of the complex sonic-components ofthe outgoing sound.

Although this figure of merit is somewhat arbitrary, it is the onlyknown method of checking the modeling of the sonic profile, generated bya speaker, or a speaker system. Even with the previous high figure ofmerit, it is entirely unsatisfactory, and this present invention allowsmodeling of the spatial/sonic distribution to be increased to a figureof merit of 75 percent, by means of multi-dimensional, total immersionstereo sound.

GENERAL DESCRIPTION In FIG. 1 is shown a typical small room 12 (e.g.,15' X 10 X 9), equipped with four sound-conditioners 13, 14, 15 and 16,according to US. Pat. No. 3,360,073, mounted in the four upper comers asshown and connected, respectively, to four separate amplifiers 17, 18,19 and 20. A multi-mixer preamplifier 21 is connected to amplifiers17-20 and a four channel tape machine 22 is connected to preamplifier21. Machine 22 includes four channel play back tape playback capability.Now provided channel No. 1, channel No. 2, channel No. 3, and channelNo. 4 are transmitting true spatial/multi-dimensional data from its fourseparate recorded channels, which were properly related each to theother at the time of recording, true stereo determined sound will beheard anywhere in the room, and as the listener 23 moves around, thesound will vary similar to that of a holosonigraph with athree-dimensional effect. If it is not correctly recorded, this will notbe true. To achieve correct recording, I propose the following:

Replace each of the sound-conditioner speakers located in the fourcorners US. Pat. No. 3,360,073) by four pickup microphones locatedinside specially modified tri-surface corner enclosures, as shown inFIG. 2, using this room, or another studio of its same insidedirnensions (15' X 10' X 9'), being sure to use a sound-conditionerdevice for the microphone (to preserve the vital XzYzZ components neededto preserve the 3-dimensionality of the sound during recording), wewould record a spatially determined multi-dimension stereo model of anysound appearing in that chamber. Then, as shown in FIG. 3, all discretesonic components, from wherever derived either directly or secondarilyin the recording chamber, will be recorded on the four-channel recorderas 1st order 4-dimensionality data along with higher orderndimensionality data (due to the multitude of reflections, absorptions,etc., in the chamber).

FIG. 2 is a sectional view through the pickup 27 mounted to adjacentwalls 24 and 25. The microphone 26 is mounted on a support 28 behindconditioning cone 29.

FIG. 3, we see in room 30 that sound from the sonic point A travelsdistances a 0 ,0 and a so as to arrive at microphones 31, 32, 33 and 34,respectively. In the examples (sound from emitter point A), thesedistances are 6%, 11%, 11%, and 6%. In a like manner, sound from point Bcould be coded as b 8', b -IO, 11 -10, and b.,8'. The variation indistance from the sound source to the several microphones 31-34 are evenmore diversified in the case of a doubly offset sound source, such asthat of point C. Point C" sounds, spatial distance wise, may be coded asfollows: c -10%', 0 -9, 0 -8. Then if we take, as but one example, asound wave at a low frequency of 32.7 c.p.s., which will have a wavelength of 34.5 feet, then the condition illustrated in FIG. 22 wouldtake place, if this wave started from point C.

The amount of phase variation as shown in FIG. 22 is readily detected,and it is this which gives the various homes, studios, theaters, andauditoriums their coloration and atonality; since we must remember thatthese chambers will be constantly reflecting, absorbing, and reinforcingthe various components of the complex sounds that impinge on theirwalls, ceilings, and floors, and 'onto and from the materials with whichthey are covered. Notice that the wave, when it is long, as in thiscase, is linearly sampled at four distinct points by the fourmicrophones.

The situation becomes even more complex as the frequency of transmissionincreases somewhat. For example, if the wave has a frequency of 112.8c.p.s., then its wave length would be 10 feet and we would have thesituation illustrated in FIG. 23.

We see that with microphone 31, we will have a zero amplitude input forrecording on our channel No. 1 (at this time), while with microphones32, 33, and 34, we

are at a somewhat less than maximum pressure amplitude (at the sametime), which will be recorded on our channels No. 2, No. 3, and No. 4recordings. All of which implies, that we can quite precisely provide11"- dimensional modeling of the sonic energy inside a chamber, if weuse the corner locations as microphone pickup regions, and also as theplayback points, and if the room in which the playback is made isidentical in volume dimensionality to that of the recording room. Inthis case, we will achieve a true holostereogram (entirely solid record)reproduction of the original (a replicate) with all the overtones,second order reflections and reverberations, and higher order effects.It is assumed, of course, that the input sensors, the transfer audiosystem, the recorders, the amplifiers, and the playback reproducers thatare used, preserve the many other important aspects of the sonicn"-dimensioned matrix, such as frequency, fidelity, balance, level, etc.

It further should be obvious that if microphones are placed elsewhere,than in the corners of the recording volume, even if the speakers areplaced in the identical locations in the reproduction room, we cannotachieve true stereo, or fidelity, since the n"-ordered components willnot be permitted to obey the three-dimensionality of space, as set forthearlier. If the speakers are not located in the same place as themicrophones, then of course all effort to reproduce the original soundis futile; as is also the case when the microphones are indiscriminatelyplaced, but the speakers are correctly located. Some results in the pasthave been achieved with attempts at sonic modeling of the recordingchamber; but, as can be anticipated, use was made only of the firstorder dimensionality sonic energy.

Thus, no combination of microphones, placed in any manner, in anystudio, theater, or auditorium, can be used, which will capture then"-dimensionality spatial relationships of the recording-volume made useof, for the recording and later reproduction of the sound in it, exceptwhen we place them in an upper comer and use a geometrically determinedidentical room, which we provide elsewhere. Thus, any effort to maintainthe spatial relationship in an oblong room when the original recordingwas made in a truncated chamber is hopeless. Even if the cornermicrophone technique is used, there is no guarantee that the homelistener will place his speakers in an identical position, and in fact,

and in most cases, it is not possible; nor, can one pick the proper, orbest place, since furniture and other bric-a-brac will invariablyintervene. With the use of the upper microphone/speaker cornertechnique, true modeled stereo, which duplicates the original, is nowpossible.

I shall now show how this is indeed possible, and how we additionallycan time-model small listening rooms in which most recordings are playedback, in such a manner so as to duplicate the original studio or otherrecording location. Indeed, it is possible not only to compress andexpand the volume of a small room at will, by time-modeling, but toachieve purposely distorted and highly interesting effects by thistechnique.

FIG. 4 illustrates four microphone sound-conditioners 31-34 located inthe corners of the recording studio 30, auditorium or hall similar tothat in FIG. 3. A recorder 36 has 4 distinct and separate recordingsystems which will produce four separate tracks of taped materials37-40, one from each channel which are respectively connected tomicrophones 31-34.

FIG. 5 illustrates separate amplifiers 41-44 for playback of therecordings, each of which will make use of one of the tapes 37-40 madeon recorder 36. Each amplifier 41-44 will have its own volume, balance,high/low boast controls, etc. We will identify channel No. 1, as RT,,,or the Record at Time Zero channel, and channel No. 1,, the PT or thePlayback at Time Zero channel, etc. Amplifiers 41-44 are respectivelyconnected to comer speakers 46-49 according to U.S. Pat. No. 3,360,073mounted in room 50.

Now since from any point P,, P,, P, P,,, (FIG. 6), in the recordingvolume different arrival times of the sound from any point will berecorded by the pickups, if we call one channel RT,, and assume that thesequence of events start at T then RT,, RT,, and RT will have aspatialltime/displacement equivalent to the physical distance that thesonic waves travel at a velocity of approximately 1,128 feet per second.Let us assume that the studio of FIG. 6 is 30 X 20' X 9' in itsdimensions and we have a point sound source at P then for sound to gofrom RT,, (P to RT (P would take 26.4 milli-seconds to arrive at pointRT,; 31.7 milli-seconds to arrive at RT and 17.7 multi-seconds to arriveat RT,,. This is shown in FIG. 7.- But, since our replay room FIG. 8 isonly 15' X 10' X 9', or one-half of these dimensions in theleft-to-right, and front-toback dimensions, the sound would be projectedback to any listener much too fast (see FIG. 9), and, as is actuallyobserved, would be unsatisfactory to a great extent, since we havecompletely destroyed the second order time variant reverberantcharacteristics of the original sound. If, however, we make arrangementsto insure that we delay each of the non-PT channels, i.e., PT,, PT,, andPT;,, by an amount equal in delay, in this case, to one-half of thespatial time factor, we will recreate the original dimensions, as far asan observer in that particular volume (m"), is concerned. We simplyplace each tape 37-40 on the channel 1, 2, 3, and 4 machines 41-44 insuch a manner that their separate sounds are slightly late in beingreplayed, by

course, depend on the tape speed used by the replay channel. Forexample:

At a tape speed of 7.5 inches per second, we have A plus displacement ofPT of 0.099 inch on a linear line A plus displacement of PT, of 0.119inch on a linear line A plus displacement of P1: of 0.066 inch on alinear line. While these amounts of rotary displacement may seem smallto attempt to physically displace an 8 inch diameter reel, for example,they could be achieved if necessary; however, better and more adequatemethods are available for actual production of usable devices.Nevertheless, the entire principle can be demonstrated as shown, with nospecial equipment being necessary. In the milli-second delay region thatis required, a normal type set-delay knob, (in FIG. marked 51, 52, 53and 54 could be used to actually rotate the four reel holders onmachines 41-44 by a very slight amount if required and the effect wouldbe achieved. Alternatively, the various playback heads, 55-58 of themachines could be easily displaced along the tape tracking path by theseamounts to achieve the same effect.

If the recording studio had been an auditorium of say, 180' X I20, thensince these dimensions are far larger (about 12 times as large as thoseof the playback chamber) we must increase the playback room (by means ofour sonic space Compander") by an amount equal to the increased lineardelay time that would be required to sonically change the dimensions ofthe listening room. This will require the following changes in therelative displacement of the tape heads (referred to PT FIG. 8):

A plus displacement of PT, by 0.495inch A plus displacement of PT by0.714 inch A plus displacement of PT by 0.396 inch.

Thus, we can make our small room of 20' X 10 X 9' into a 180 X 120'auditorium, or indeed, into any size we choose, simply by turning thetapes, or moving the playback heads relative to a common reference pointPR As proposed herein, there may be a slight error in the verticaltop-to-bottom dimension, which can be corrected on the tape directly atthe time of recording with little error resulting, due to the fact thatmost playback rooms will be very close to 9 feet in height (7 feet to 12feet on the average). It is of course possible to compromise quiteseverely, and build-in the delays on a somewhat average basis for thevarious recording chambers, and assume that the listening volume willhave an average spatial size of say 15 X 12' X 9' as was done for thevertical dimension and still obtain good results.

FIGS. 10 and 11 illustrate a system for directly and instantly achievingthe modeling-effect, wherein a single four-track tape recorder 55 isused to assure rotational-time synchronization at the recording studio.This means that our four track recording will have all the ri-dimensional spatial data on it, keyed to the dimensions of therecording studios volume, and provided we use our corner microphonepickups 56-59 and our corner playback speakers, 60-63 (see FIG. 11), wecan scale the ri -dimensionality factors down or up, as we desire, bydelaying the various channels relative to each other. We show fourcontrol knobs 65-68 on the playback machine 64 whose attached mechanismsmove the playback heads along each separate track relative to each otherso as to achieve the appropriate and required delay, thus accomplishingthe necessary time sculpturing of the original sonic data.

This method can be installed on existing-type tape recorders with easeand slight modifications; however, a separate auxiliary system can beused to advantage with a resulting increase in the ease and precision ofsculpturing the sound in the listening volume to that of the originalrecording volume.

FIG. 12 illustrates a modification in which a tape machine has magnetictape 71 carried by rollers 72, 73, 74 and 75. An erase head 76 andspaced record heads 77, 78, 79 and 80 are mounted on the machine 70.Playback heads 81, 82, 83 and 84 are adjustably mounted on shaft 86relative to the tape 71 to obtain variable delay. To obtain easierprecise control of the displacement, we use tape at band speeds up to 15inches per second. This will give a displacement variation of from 0.15inch to about 1.5 inches for movement of the heads. The replay heads 81,82, 83 and 84 may be adjusted on shaft 86 by knobs 87, 88, 89 and 90. Asshown in FIG. 13 the tape 71 has four bands 91, 92, 93 and 94 and a pairof record and playback heads are associated with the track.

FIG. 14 illustrates a modification in which we use a flat magnetizabledisc 95, containing four bands of imbedded magnetic material 96, 97 98and 99. Erase heads 100-103 are mounted on fixed arm 104 and recordheads 105-108 are mounted on fixed arm 109. Movable arms 110, 111, 112and 113 respectively carry playback heads 114-117 which are aligned withbands 96-99. The position of arms -113 may be selectively adjusted toobtain the advantages of the invention. It should be noted that byjudicious selection of the tracks on the various bands, we can decreasethe necessity to allow for the difference in true velocity pass the headof the peripheral bands to some extent. Note this in the ordering of thereplay bands, wherein band 97 may be taken as PT band 96 is taken as PTband 98 is taken as P1 and finally band 99 as PT FIG. 15 illustratesanother modification in whicha magnetic drum 115 has bands 116-119 ofimbedded magnetizable ferro-material on the cylindrical surface. Recordheads 120-123 are mounted over bands 116-119 and permanent magnet erasehead 124 erases all tracks. Playback heads 126-129 are mounted onmovable brackets 130-133. The drum 115 driven by belt 136 which passesover pulleys 134 and 137. All heads are in the same curved plane,relative to the axis 138 of rotation. Various delays can be obtained bysimple rotation of the pickup heads by moving the brackets 130-133 backand forth relative to each other. Note that a negative time, cantheoretically be placed into the system if desired.

The three systems illustrated in FIGS. 12-15 will have the same need forthe same band speeds past the pickup heads of the recorded material andof the same order of magnitude, and for the same amount of displacementeach from the other, depending on the control of that speed, to effectthe necessary precise sculpturing of the eminent sound.

Thus, it is seen that we can literally carve-out a solidity (stereo) ofsound, to the degree we wish and that we can shrink, expand, or evendistort the resulting amount of sculpturing as desired. We can also,actually move the location of the original sonic source around ourlistening volume to any place that we so choose. It is necessary todelimit the sound reception of any specific volume by use of the at itslirni limiting sonic-pickups, and do the same for the playback roomvolume.

It is difficult to duplicate the sound components of an auditorium in asmall room if the primary recording volume is highly non-structured inthe first place. However, if recording is done in a pie-shapedauditorium as shown in FIG. 16, compensation and seulpturing of thelistening volume by a mere adjustment of the delay controls may beaccomplished since distances d and d, will be determined by D, D whichcan be placed into the delay channels as a negative override, ifrequired. FIG. 17 illustrates an actual listening volume 140 in thecorners of which the sounders have been mounted which appears as thelarger pie-shaped area.

In FIGS. 18 and 19 an embodiment of the principle of time/spatialsonic-modeling as applied to a regular dual disc-type recording isshown. In this case, the record 141 has a standard bi-lateral, stereogroove 142 in which record channels 1 and 2 are recorded, and anadjacent stereo groove, also of bilateral stereo, for channels 3 and 4are recorded. The tone arm 143 instead of using a single needle forpicking up the first and second channels of stereo, (since this wouldprovide only a zero time displacement at that point), uses a doubleneedle in a single or double cartridge. Each of 1 these may then bedisplaced relative to each other and to the other double-needledcartridge in the adjacent channel. Needles 144 and 147 rest in onegroove 142 of the record disc while needles 146 and 146 rest in theadjacent groove. Therefore, bilateral, adjacent groove, horizontalrecording allows achievement of the four channel effects desired. Theneedles 144-147 may be respectively adjusted by screws 148-151 for thedelay setting.

Thus, this invention results from the realization that sound is a3-dimensional phenomenon, which when recorded in any chamber becomes ann"-dimensioned resultant (due to the multiple additions and reflections,as well as selective absorptions). By providing recording and playbackequipment as shown which takes these facts severely into account, trueholostereo (solidity) sculpturing of the sonic materials far superior toany stereo system previously in existence is obtained. The inventionalso allows replication or duplication of the originaltime/spatial-dimensions of the original recording chamber, thereby trulyachieving a faithful duplicate of the sonic matrix created in thatoriginal recording chamber. Indeed, if desired, even nonfaithful, butnevertheless, intriguing effects can be obtained wherein one literallyrotates or moves the orchestra or singers around at will.

It should be understood that various modifications to the method andtechniques as herein shown can be made without departing from the spiritor intent of the inventions novelty or scope.

I claim:

1. A system and apparatus for recording and playing back sound whichduplicates the volume of the original recording space and wherein thevolume of the original recording space differs from the volume of theplayback space comprising:

means for recording sound in said recording space on a plurality ofrecording channels each associated with discrete and different positionsin said recording space and including a plurality of microphones eachmounted in tri-portal, tri-planal enclosures mounted respectively inupper comers adjacent the ceiling of the recording space;

means for reproducing in said playback space including a plurality ofback fill-in speakers each mounted in tri-portal, tri-planal enclosuresmounted respectively in upper corners adjacent the ceiling of theplayback space and said microphones and speakers mounted incorresponding positions and said speakers receiving the recordingchannel associated with said microphone located at its correspondingposition; and

a plurality of time delay means respectively mounted in each recordingchannel between the associated microphone and speaker such that saidtime delay introduced in each channel is determined by the relativedimensions of said recording space and playback space and the positionsof corresponding microphones and speakers so as to duplicate the nthdimensionality of the recording space.

2. A system and apparatus according to claim 1, wherein said means forrecording comprises four microphones and said sound reproducing meanscomprises four speakers respectively mounted in the upper corners of therecording space and playback space.

3. A system and apparatus according to claim 2 wherein said means forrecording includes a phonographic recording means formed with aplurality of recording channels.

4. A system and apparatus according to claim 3 wherein said phonographicrecording means is a disc with two separate recording grooves each ofwhich contain two channels of information.

5. A system and apparatus according to claim 4 wherein said means forreproducing includes a plurality of styluses receivable in said'separate recording grooves to pick up the various channels ofinformation and means for adjusting said styluses relative to eachother.

6. A system and apparatus according to claim 2 wherein said means forrecording comprises a magnetic recorder with a plurality of recordingheads for recording said different recording channels.

7. A system and apparatus according to claim 6 wherein said magneticrecorder is a magnetic tape device and said sound reproducing means is amagnetic tape device with a plurality of playback heads and saidplurality of time delay means comprises means for adjusting thepositions of said playback heads.

8. A system and apparatus according to claim 6 wherein said magneticrecorder is a flat magnetic disc device with a plurality of recordingheads for recording different recording channels and said soundreproducing means receives said flat magnetic disc and has a pluralityof playback heads and said plurality of time delay means comprises meansfor adjusting the angular positions of said playback heads relative tosaid disc.

9. A system and apparatus according to claim 6 wherein said magneticrecorder is a magnetic drum device with a plurality of recording headsfor recording different recording channels and said sound reproducingmeans receives said drum and has a plurality of playback heads and saidtime delay means comprises means for adjusting the positions of saidplayback heads about said drum.

10. A system and apparatus according to claim 9 comprising a pluralityof arms upon which said playback heads are mounted and means foradjusting and holding said arms in various positions.

UNITED STATES PATENT QFFICE CERTIFICATE OF Patent No.. 3, 710', 034

Inventor(s) Edward I. Murry It is certified that error appears and thatsaid Letters Patent are hereby Column 3, line 55, change the equation8e'/3 2.3 A A Column 4, line 13, change the equation e AX Ay AZ au/at 4,line 20, change the equation and by replacing the Column Column 4, line33, change the equation als /8 A A y Z,

Column CORRECTIQN Dated January 9, 1973 in the above-identified patentcorrected as shown below:

as follows: I

as follows:

by replacing the with with as follows:

4, line 34, change the equations as follows:

EEO/3y Ar Ay AZ, oraeo/az Ax Ay AZ Column 8, line 43, change the to andc 9 l/4'.--.

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. Attesting Officer.

ORM PO-105O (10-69) C. MARSHALL DANN ommissioner of P item ts

1. A system and apparatus for recording and playing back sound which duplicates the volume of the original recording space and wherein the volume of the original recording space differs from the volume of the playback space comprising: means for recording sound in said recording space on a plurality of recording channels each associated with discrete and different positions in said recording space and including a plurality of microphones each mounted in tri-portal, tri-planal enclosures mounted respectively in upper corners adjacent the ceiling of the recording space; means for reproducing in said playback space including a plurality of back fill-in speakers each mounted in tri-portal, tri-planal enclosures mounted respectively in upper corners adjacent the ceiling of the playback space and said microphones and speakers mounted in corresponding positions and said speakers receiving the recording channel associated with said microphone located at its corresponding position; and a plurality of time delay means respectively mounted in each recording channel between the associated microphone and speaker such that said time delay introduced in each channel is determined by the relative dimensions of said recording space and playback space and the positions of corresponding microphones and speakers so as to duplicate the nth dimensionality of the recording space.
 2. A system and apparatus according to claim 1, wherein said means for recording comprises four microphones and said sound reproducing means comprises four speakers respectively mounted in the upper corners of the recording space and playback space.
 3. A system and apparatus according to claim 2 wherein said means for recording includes a phonographic recording means formed with a plurality of recording channels.
 4. A system and apparatus according to claim 3 wherein said phonographic recording means is a disc with two separate recording grooves each of which contain two channels of information.
 5. A system and apparatus according to claim 4 wherein said means for reproducing includes a plurality of styluses receivable in said separate recording grooves to pick up the various channels of information and means for adjusting said styluses relative to each other.
 6. A system and apparatus according to claim 2 wherein said means for recording comprises a magnetic recorder with a plurality of recording heads for recording said different recording channels.
 7. A system and apparatus according to claim 6 wherein said magnetic recorder is a magnetic tape device and said sound reproducing means is a magnetic tape device with a plurality of playback heads and said plurality of time delay means comprises means for adjusting the positions of said playback heads.
 8. A system and apparatus according to claim 6 wherein said magnetic recorder is A flat magnetic disc device with a plurality of recording heads for recording different recording channels and said sound reproducing means receives said flat magnetic disc and has a plurality of playback heads and said plurality of time delay means comprises means for adjusting the angular positions of said playback heads relative to said disc.
 9. A system and apparatus according to claim 6 wherein said magnetic recorder is a magnetic drum device with a plurality of recording heads for recording different recording channels and said sound reproducing means receives said drum and has a plurality of playback heads and said time delay means comprises means for adjusting the positions of said playback heads about said drum.
 10. A system and apparatus according to claim 9 comprising a plurality of arms upon which said playback heads are mounted and means for adjusting and holding said arms in various positions. 